The present invention relates generally to a brake control system for an automotive vehicle, which controls braking pressure at the front and rear wheels independently. More specifically, the invention relates to an automotive brake control system which controls yawing of vehicle by adjusting the braking force on the front and rear wheels independently, and thereby affords the vehicle good steering characteristics.
In the recent years, various anti-skid brake control systems for automotive vehicles have been developed. Among these systems, some control braking pressure at each wheel independently. Although such anti-skid brake control systems were developed specifically to optimize braking characteristics by preventing the vehicular wheels from locking, they are also known to provide greater cornering force so as to help prevent vehicle spinning, even when the brakes are applied during cornering.
In these prior art systems, anti-skid brake control is generally performed under low-friction, slippery road surface conditions, such as roads covered with snow, ice and so forth, on which vehicular wheels tend to skid easily. On the other hand, when road/tire friction is high enough, anti-skid brake control systems frequently remain inactive. On relatively high-friction road surfaces, the brake feeling is substantially the same as during manual braking even when the anti-skid control systems are indeed active. However, even under high-friction road conditions, vehicular wheels may slip when the brakes are applied during cornering. This slip decreases the cornering force and thus adversely affects the steering characteristics of the vehicle. For instance, when the vehicular cornering speed is relatively high, wheel slip may be sufficiently bad to allow over-steering effects such as tack-in or spin as the centrifugal force overcomes the cornering force. In such cases, the vehicle can go out of control.